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Date: Tue, 10 May 2022 12:21:54 -0700
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Shuah Khan <shuah@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Michal Hocko <mhocko@...nel.org>
Cc: Stanislav Fomichev <sdf@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Greg Thelen <gthelen@...gle.com>,
Shakeel Butt <shakeelb@...gle.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
cgroups@...r.kernel.org
Subject: Re: [RFC PATCH bpf-next 1/9] bpf: introduce CGROUP_SUBSYS_RSTAT
program type
On Tue, May 10, 2022 at 11:07 AM Yosry Ahmed <yosryahmed@...gle.com> wrote:
>
> On Mon, May 9, 2022 at 5:18 PM Yosry Ahmed <yosryahmed@...gle.com> wrote:
> >
> > This patch introduces a new bpf program type CGROUP_SUBSYS_RSTAT,
> > with new corresponding link and attach types.
> >
> > The main purpose of these programs is to allow BPF programs to collect
> > and maintain hierarchical cgroup stats easily and efficiently by making
> > using of the rstat framework in the kernel.
> >
> > Those programs attach to a cgroup subsystem. They typically contain logic
> > to aggregate per-cpu and per-cgroup stats collected by other BPF programs.
> >
> > Currently, only rstat flusher programs can be attached to cgroup
> > subsystems, but this can be extended later if a use-case arises.
> >
> > See the selftest in the final patch for a practical example.
> >
> > Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
> > ---
> > include/linux/bpf-cgroup-subsys.h | 30 ++++++
> > include/linux/bpf_types.h | 2 +
> > include/linux/cgroup-defs.h | 4 +
> > include/uapi/linux/bpf.h | 12 +++
> > kernel/bpf/Makefile | 1 +
> > kernel/bpf/cgroup_subsys.c | 166 ++++++++++++++++++++++++++++++
> > kernel/bpf/syscall.c | 6 ++
> > kernel/cgroup/cgroup.c | 1 +
> > tools/include/uapi/linux/bpf.h | 12 +++
> > 9 files changed, 234 insertions(+)
> > create mode 100644 include/linux/bpf-cgroup-subsys.h
> > create mode 100644 kernel/bpf/cgroup_subsys.c
> >
> > diff --git a/include/linux/bpf-cgroup-subsys.h b/include/linux/bpf-cgroup-subsys.h
> > new file mode 100644
> > index 000000000000..4dcde06b5599
> > --- /dev/null
> > +++ b/include/linux/bpf-cgroup-subsys.h
> > @@ -0,0 +1,30 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright 2022 Google LLC.
> > + */
> > +#ifndef _BPF_CGROUP_SUBSYS_H_
> > +#define _BPF_CGROUP_SUBSYS_H_
> > +
> > +#include <linux/bpf.h>
> > +
> > +struct cgroup_subsys_bpf {
> > + /* Head of the list of BPF rstat flushers attached to this subsystem */
> > + struct list_head rstat_flushers;
> > + spinlock_t flushers_lock;
> > +};
> > +
> > +struct bpf_subsys_rstat_flusher {
> > + struct bpf_prog *prog;
> > + /* List of BPF rtstat flushers, anchored at subsys->bpf */
> > + struct list_head list;
> > +};
> > +
> > +struct bpf_cgroup_subsys_link {
> > + struct bpf_link link;
> > + struct cgroup_subsys *ss;
> > +};
> > +
> > +int cgroup_subsys_bpf_link_attach(const union bpf_attr *attr,
> > + struct bpf_prog *prog);
> > +
>
> In the next version I will make sure everything here is also defined
> for when CONFIG_BPF_SYSCALL is not set, and move the structs that can
> be moved to the cc file there.
>
> > +#endif // _BPF_CGROUP_SUBSYS_H_
> > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> > index 3e24ad0c4b3c..854ee958b0e4 100644
> > --- a/include/linux/bpf_types.h
> > +++ b/include/linux/bpf_types.h
> > @@ -56,6 +56,8 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SYSCTL, cg_sysctl,
> > struct bpf_sysctl, struct bpf_sysctl_kern)
> > BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCKOPT, cg_sockopt,
> > struct bpf_sockopt, struct bpf_sockopt_kern)
> > +BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT, cgroup_subsys_rstat,
> > + struct bpf_rstat_ctx, struct bpf_rstat_ctx)
> > #endif
> > #ifdef CONFIG_BPF_LIRC_MODE2
> > BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2,
> > diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
> > index 1bfcfb1af352..3bd6eed1fa13 100644
> > --- a/include/linux/cgroup-defs.h
> > +++ b/include/linux/cgroup-defs.h
> > @@ -20,6 +20,7 @@
> > #include <linux/u64_stats_sync.h>
> > #include <linux/workqueue.h>
> > #include <linux/bpf-cgroup-defs.h>
> > +#include <linux/bpf-cgroup-subsys.h>
> > #include <linux/psi_types.h>
> >
> > #ifdef CONFIG_CGROUPS
> > @@ -706,6 +707,9 @@ struct cgroup_subsys {
> > * specifies the mask of subsystems that this one depends on.
> > */
> > unsigned int depends_on;
> > +
> > + /* used to store bpf programs.*/
> > + struct cgroup_subsys_bpf bpf;
> > };
> >
> > extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index d14b10b85e51..0f4855fa85db 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -952,6 +952,7 @@ enum bpf_prog_type {
> > BPF_PROG_TYPE_LSM,
> > BPF_PROG_TYPE_SK_LOOKUP,
> > BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> > + BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT,
> > };
> >
> > enum bpf_attach_type {
> > @@ -998,6 +999,7 @@ enum bpf_attach_type {
> > BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
> > BPF_PERF_EVENT,
> > BPF_TRACE_KPROBE_MULTI,
> > + BPF_CGROUP_SUBSYS_RSTAT,
> > __MAX_BPF_ATTACH_TYPE
> > };
> >
> > @@ -1013,6 +1015,7 @@ enum bpf_link_type {
> > BPF_LINK_TYPE_XDP = 6,
> > BPF_LINK_TYPE_PERF_EVENT = 7,
> > BPF_LINK_TYPE_KPROBE_MULTI = 8,
> > + BPF_LINK_TYPE_CGROUP_SUBSYS = 9,
> >
> > MAX_BPF_LINK_TYPE,
> > };
> > @@ -1482,6 +1485,9 @@ union bpf_attr {
> > */
> > __u64 bpf_cookie;
> > } perf_event;
> > + struct {
> > + __u64 name;
> > + } cgroup_subsys;
> > struct {
> > __u32 flags;
> > __u32 cnt;
> > @@ -6324,6 +6330,12 @@ struct bpf_cgroup_dev_ctx {
> > __u32 minor;
> > };
> >
> > +struct bpf_rstat_ctx {
> > + __u64 cgroup_id;
> > + __u64 parent_cgroup_id; /* 0 if root */
> > + __s32 cpu;
> > +};
> > +
> > struct bpf_raw_tracepoint_args {
> > __u64 args[0];
> > };
> > diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> > index c1a9be6a4b9f..6caf4a61e543 100644
> > --- a/kernel/bpf/Makefile
> > +++ b/kernel/bpf/Makefile
> > @@ -25,6 +25,7 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
> > obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
> > endif
> > obj-$(CONFIG_CGROUP_BPF) += cgroup.o
> > +obj-$(CONFIG_CGROUP_BPF) += cgroup_subsys.o
>
> In the next version I will replace this with:
> ifeq ($(CONFIG_CGROUP),y)
> obj-$(CONFIG_BPF_SYSCALL) += cgroup_subsys.o
> endif
>
> , as this program type doesn't attach to cgroups and does not depend
> on CONFIG_CGROUP_BPF, only CONFIG_CGROUP and CONFIG_BPF_SYSCALL.
On second thought it might be simpler and cleaner to leave this code
under CONFIG_CGROUP_BPF.
>
> > ifeq ($(CONFIG_INET),y)
> > obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
> > endif
> > diff --git a/kernel/bpf/cgroup_subsys.c b/kernel/bpf/cgroup_subsys.c
> > new file mode 100644
> > index 000000000000..9673ce6aa84a
> > --- /dev/null
> > +++ b/kernel/bpf/cgroup_subsys.c
> > @@ -0,0 +1,166 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Functions to manage eBPF programs attached to cgroup subsystems
> > + *
> > + * Copyright 2022 Google LLC.
> > + */
> > +
> > +#include <linux/bpf-cgroup-subsys.h>
> > +#include <linux/filter.h>
> > +
> > +#include "../cgroup/cgroup-internal.h"
> > +
> > +
> > +static int cgroup_subsys_bpf_attach(struct cgroup_subsys *ss, struct bpf_prog *prog)
> > +{
> > + struct bpf_subsys_rstat_flusher *rstat_flusher;
> > +
> > + rstat_flusher = kmalloc(sizeof(*rstat_flusher), GFP_KERNEL);
> > + if (!rstat_flusher)
> > + return -ENOMEM;
> > + rstat_flusher->prog = prog;
> > +
> > + spin_lock(&ss->bpf.flushers_lock);
> > + list_add(&rstat_flusher->list, &ss->bpf.rstat_flushers);
> > + spin_unlock(&ss->bpf.flushers_lock);
> > +
> > + return 0;
> > +}
> > +
> > +static void cgroup_subsys_bpf_detach(struct cgroup_subsys *ss, struct bpf_prog *prog)
> > +{
> > + struct bpf_subsys_rstat_flusher *rstat_flusher = NULL;
> > +
> > + spin_lock(&ss->bpf.flushers_lock);
> > + list_for_each_entry(rstat_flusher, &ss->bpf.rstat_flushers, list)
> > + if (rstat_flusher->prog == prog)
> > + break;
> > +
> > + if (rstat_flusher) {
> > + list_del(&rstat_flusher->list);
> > + bpf_prog_put(rstat_flusher->prog);
> > + kfree(rstat_flusher);
> > + }
> > + spin_unlock(&ss->bpf.flushers_lock);
> > +}
> > +
> > +static void bpf_cgroup_subsys_link_release(struct bpf_link *link)
> > +{
> > + struct bpf_cgroup_subsys_link *ss_link = container_of(link,
> > + struct bpf_cgroup_subsys_link,
> > + link);
> > + if (ss_link->ss) {
> > + cgroup_subsys_bpf_detach(ss_link->ss, ss_link->link.prog);
> > + ss_link->ss = NULL;
> > + }
> > +}
> > +
> > +static int bpf_cgroup_subsys_link_detach(struct bpf_link *link)
> > +{
> > + bpf_cgroup_subsys_link_release(link);
> > + return 0;
> > +}
> > +
> > +static void bpf_cgroup_subsys_link_dealloc(struct bpf_link *link)
> > +{
> > + struct bpf_cgroup_subsys_link *ss_link = container_of(link,
> > + struct bpf_cgroup_subsys_link,
> > + link);
> > + kfree(ss_link);
> > +}
> > +
> > +static const struct bpf_link_ops bpf_cgroup_subsys_link_lops = {
> > + .detach = bpf_cgroup_subsys_link_detach,
> > + .release = bpf_cgroup_subsys_link_release,
> > + .dealloc = bpf_cgroup_subsys_link_dealloc,
> > +};
> > +
> > +int cgroup_subsys_bpf_link_attach(const union bpf_attr *attr,
> > + struct bpf_prog *prog)
> > +{
> > + struct bpf_link_primer link_primer;
> > + struct bpf_cgroup_subsys_link *link;
> > + struct cgroup_subsys *ss, *attach_ss = NULL;
> > + const char __user *ss_name_user;
> > + char ss_name[MAX_CGROUP_TYPE_NAMELEN];
> > + int ssid, err;
> > +
> > + if (attr->link_create.target_fd || attr->link_create.flags)
> > + return -EINVAL;
> > +
> > + ss_name_user = u64_to_user_ptr(attr->link_create.cgroup_subsys.name);
> > + if (strncpy_from_user(ss_name, ss_name_user, sizeof(ss_name) - 1) < 0)
> > + return -EFAULT;
> > +
> > + for_each_subsys(ss, ssid)
> > + if (!strcmp(ss_name, ss->name) ||
> > + !strcmp(ss_name, ss->legacy_name))
> > + attach_ss = ss;
> > +
> > + if (!attach_ss)
> > + return -EINVAL;
> > +
> > + link = kzalloc(sizeof(*link), GFP_USER);
> > + if (!link)
> > + return -ENOMEM;
> > +
> > + bpf_link_init(&link->link, BPF_LINK_TYPE_CGROUP_SUBSYS,
> > + &bpf_cgroup_subsys_link_lops,
> > + prog);
> > + link->ss = attach_ss;
> > +
> > + err = bpf_link_prime(&link->link, &link_primer);
> > + if (err) {
> > + kfree(link);
> > + return err;
> > + }
> > +
> > + err = cgroup_subsys_bpf_attach(attach_ss, prog);
> > + if (err) {
> > + bpf_link_cleanup(&link_primer);
> > + return err;
> > + }
> > +
> > + return bpf_link_settle(&link_primer);
> > +}
> > +
> > +static const struct bpf_func_proto *
> > +cgroup_subsys_rstat_func_proto(enum bpf_func_id func_id,
> > + const struct bpf_prog *prog)
> > +{
> > + return bpf_base_func_proto(func_id);
> > +}
> > +
> > +static bool cgroup_subsys_rstat_is_valid_access(int off, int size,
> > + enum bpf_access_type type,
> > + const struct bpf_prog *prog,
> > + struct bpf_insn_access_aux *info)
> > +{
> > + if (type == BPF_WRITE)
> > + return false;
> > +
> > + if (off < 0 || off + size > sizeof(struct bpf_rstat_ctx))
> > + return false;
> > + /* The verifier guarantees that size > 0 */
> > + if (off % size != 0)
> > + return false;
> > +
> > + switch (off) {
> > + case offsetof(struct bpf_rstat_ctx, cgroup_id):
> > + return size == sizeof(__u64);
> > + case offsetof(struct bpf_rstat_ctx, parent_cgroup_id):
> > + return size == sizeof(__u64);
> > + case offsetof(struct bpf_rstat_ctx, cpu):
> > + return size == sizeof(__s32);
> > + default:
> > + return false;
> > + }
> > +}
> > +
> > +const struct bpf_prog_ops cgroup_subsys_rstat_prog_ops = {
> > +};
> > +
> > +const struct bpf_verifier_ops cgroup_subsys_rstat_verifier_ops = {
> > + .get_func_proto = cgroup_subsys_rstat_func_proto,
> > + .is_valid_access = cgroup_subsys_rstat_is_valid_access,
> > +};
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index cdaa1152436a..48149c54d969 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -3,6 +3,7 @@
> > */
> > #include <linux/bpf.h>
> > #include <linux/bpf-cgroup.h>
> > +#include <linux/bpf-cgroup-subsys.h>
> > #include <linux/bpf_trace.h>
> > #include <linux/bpf_lirc.h>
> > #include <linux/bpf_verifier.h>
> > @@ -3194,6 +3195,8 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
> > return BPF_PROG_TYPE_SK_LOOKUP;
> > case BPF_XDP:
> > return BPF_PROG_TYPE_XDP;
> > + case BPF_CGROUP_SUBSYS_RSTAT:
> > + return BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT;
> > default:
> > return BPF_PROG_TYPE_UNSPEC;
> > }
> > @@ -4341,6 +4344,9 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
> > else
> > ret = bpf_kprobe_multi_link_attach(attr, prog);
> > break;
> > + case BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT:
> > + ret = cgroup_subsys_bpf_link_attach(attr, prog);
> > + break;
> > default:
> > ret = -EINVAL;
> > }
> > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> > index adb820e98f24..7b1448013009 100644
> > --- a/kernel/cgroup/cgroup.c
> > +++ b/kernel/cgroup/cgroup.c
> > @@ -5745,6 +5745,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
> >
> > idr_init(&ss->css_idr);
> > INIT_LIST_HEAD(&ss->cfts);
> > + INIT_LIST_HEAD(&ss->bpf.rstat_flushers);
> >
> > /* Create the root cgroup state for this subsystem */
> > ss->root = &cgrp_dfl_root;
> > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> > index d14b10b85e51..0f4855fa85db 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -952,6 +952,7 @@ enum bpf_prog_type {
> > BPF_PROG_TYPE_LSM,
> > BPF_PROG_TYPE_SK_LOOKUP,
> > BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> > + BPF_PROG_TYPE_CGROUP_SUBSYS_RSTAT,
> > };
> >
> > enum bpf_attach_type {
> > @@ -998,6 +999,7 @@ enum bpf_attach_type {
> > BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
> > BPF_PERF_EVENT,
> > BPF_TRACE_KPROBE_MULTI,
> > + BPF_CGROUP_SUBSYS_RSTAT,
> > __MAX_BPF_ATTACH_TYPE
> > };
> >
> > @@ -1013,6 +1015,7 @@ enum bpf_link_type {
> > BPF_LINK_TYPE_XDP = 6,
> > BPF_LINK_TYPE_PERF_EVENT = 7,
> > BPF_LINK_TYPE_KPROBE_MULTI = 8,
> > + BPF_LINK_TYPE_CGROUP_SUBSYS = 9,
> >
> > MAX_BPF_LINK_TYPE,
> > };
> > @@ -1482,6 +1485,9 @@ union bpf_attr {
> > */
> > __u64 bpf_cookie;
> > } perf_event;
> > + struct {
> > + __u64 name;
> > + } cgroup_subsys;
> > struct {
> > __u32 flags;
> > __u32 cnt;
> > @@ -6324,6 +6330,12 @@ struct bpf_cgroup_dev_ctx {
> > __u32 minor;
> > };
> >
> > +struct bpf_rstat_ctx {
> > + __u64 cgroup_id;
> > + __u64 parent_cgroup_id; /* 0 if root */
> > + __s32 cpu;
> > +};
> > +
> > struct bpf_raw_tracepoint_args {
> > __u64 args[0];
> > };
> > --
> > 2.36.0.512.ge40c2bad7a-goog
> >
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